Self-assembly of Sr2P2O7@2D rGO nano/micro-architecture for highly durable and bendable solid-state supercapattery

Abstract

Metal pyrophosphate-based materials for supercapattery have recently attracted significant research interest due to their high energy density, structural stability, and cyclability. Despite this, the low electric conductivity of such compounds severely limits the rate efficiency of supercapattery. To address this challenge, self-assembly of strontium pyrophosphate (Sr₂P₂O₇) on 2D reduced graphene oxide (rGO) was produced (Sr₂P₂O₇@2D rGO) with varying urea and rGO proportions employing a two-stage procedure: (i) layer-by-layer (LBL) deposition of rGO nanosheets, followed by (ii) a hydrothermal method to produce strontium pyrophosphate (SP) microflakes. The effective integration of conductive rGO with Sr₂P₂O₇ flakes has been verified by structural and morphological investigation, which indicates that rGO nanosheets offer a large number of active sites, high electrical conductivity, and a wide surface area. However, when compared to the other electrodes, the optimized SP/rGO-3 hybrid electrode possesses battery-like properties, with an outstanding specific capacity of 205 mAh/g (738C/g) in 1 M KOH at a current density of 2 A/g and maintains 99 % durability after 10000 cycles. These outcomes imply a synergistically enhanced surface redox charge storage mechanism through the inclusion of rGO (optimal) and the influence of SP nano/microarchitecture, resulting in an extended cycle lifespan and remarkable electrochemical characteristics. Furthermore, a hybrid solid-state (HSS) supercapattery developed by employing SP/rGO-3 as the cathode and rGO as the anode (SP/rGO-3//rGO) achieved a maximum specific (areal) capacity of 189C/g (52 mAh/g, 133 mF cm⁻²), (areal) energy density of 42.04 Wh/kg (47.3 mWh cm⁻²), and a power density of 2755.6 W/kg (3.1 mW cm⁻²). In addition, the HSS device demonstrates remarkable long-term cyclability, retaining 96 % capacity after 10000 cycles. The present research suggests that Sr₂P₂O₇@2D rGO composites have extraordinary electrochemical properties, highlighting their potential as nano/micro-structured electrodes for future energy storage devices.